As in the above-mentioned earlier patent application, one of the main applications of the present invention lies in making implantable extender devices to operate for a determined length of time beneath the scalp in order to diminish baldness, however other applications can be envisaged for the device of the invention, whenever it is useful or necessary to stretch tissue, for example to diminish wounds, or scars, or tattoos, or pigmented naevi; it is sometimes necessary to cover the surface concerned with new skin, particularly when the previous skin has been destroyed or damaged by burning, tumors, injury, etc.
Concerning baldness, known medically as "male-pattern alopecia", which is definitive and applies to one in three of men aged 50, the only effective therapy is surgical, as follows: a portion of the healthy follicles that are genetically programmed to last throughout life is surgically redistributed, which in practice means taking hair from around the tonsure.
Various methods of intervention and specific devices are known at present, such as those described in the earlier patent application: they can be characterized by three basic techniques, namely: implants, reductions of the tonsure, and flaps. All of them consist in moving hair-carrying scalp to take the place of some or all of the bald scalp. The present invention relates to the second of those techniques, and a method of intervention is described using devices that are specifically claimed in the above-mentioned patent application No. WO 93/21849 and then in FR No. 2 715 292, having the same Applicants, so there is no need to reproduce the general introduction and detailed description thereof in the present application.
It is merely recalled that there exist at present three methods of intervention, all using the same technique of reducing the tonsure and each of them making use of specific devices. The most recent method is that developed and tested successfully since filing the above-mentioned first patent application: it describes and teaches extender devices for that purpose in particular. Such a device comprises both elastic means of outside dimensions in an active extended position such that a portion of its perimeter corresponds substantially with and underlies the edges of at least a portion of the area of tissue to be treated, and at least two hooking means, each secured to one end of the elastic means, the ends being opposite each other in the active elastic direction of said elastic means, and enabling the device to be fixed in said tissue along said edges.
The present invention relates to a novel type of elastic extender device that operates on the same principle and that is used with the same intervention method: such devices are also called "extenders" since they act by selectively stretching surface area. It can thus be recalled that by using such devices with the method in question, good results are obtained in reducing tonsure, with few surgical interventions, and throughout the duration of treatment the appearance of the head remains sufficiently acceptable to enable the person concerned to continue with any normal activity, and no follicles are destroyed by ischemia of the surface layers of the scalp unlike that which has been observed in other techniques. When extender devices are applied, advantage is taken of the ability of living tissue, such as the scalp, to be stretched in the same manner as has been performed with balloons (which constitute one of the other two above-mentioned prior art methods of intervention for reducing tonsure). However, in the present case there is a great advantage associated with the fact that the tissue or hair-carrying scalp is stretched and distorted progressively but without any increase in volume. Thus instead of the total area increasing in the same manner in all directions, area is increased in predetermined directions only. There is thus firstly no change in morphology, and in particular in the shape of the head when the scalp is involved, and secondly there is no stretching in directions that are not useful.
Also, since the active ends of the extender device can be placed exactly at the edges of the zones or areas of tissue to be treated that are to be subjected to traction in order to change area, zones that are not to be stretched are not subjected directly to said tension: thus, when stretching the scalp, there is no secondary stretching of the bald zones, thereby improving the effectiveness of the system and the speed of its action.
Nevertheless, at present with known extender systems such as those described in the above-mentioned patents, and when it is desirable to have an extender of fairly large elongation capacity in order to be able to anchor its hooking means far apart (depending on the dimensions of the area of the bald zone to be reduced), it becomes necessary to increase the length of the elastic means interconnecting the hooking systems when at rest. If the device has a large elongation coefficient, e.g. such as 200% or 300%, there will always remain between the hooking systems a rest length of the elastic means equal to L for a maximum amount of dynamic variation in stretching by the hooking systems respectively equal to 2L or 3L.